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The 2009 Alexandrium bloom

The 2009 Alexandrium bloom. Donald M. Anderson- Woods Hole Oceanographic Institution Scott Libby - Battelle, Brunswick, ME. Overview of MWRA’s Involvement. Ambient Monitoring Plan and Contingency Plan call on MWRA to support targeted Alexandrium monitoring

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The 2009 Alexandrium bloom

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  1. The 2009 Alexandrium bloom Donald M. Anderson- Woods Hole Oceanographic Institution Scott Libby - Battelle, Brunswick, ME

  2. Overview of MWRA’s Involvement • Ambient Monitoring Plan and Contingency Plan call on MWRA to support targeted Alexandrium monitoring • Development of the Alexandrium Rapid Response Plan • Gain a better understanding of bloom dynamics and • Evaluate the potential impact of MWRA outfall • MWRA has conducted Alexandrium focused sampling the last five years • Often in conjunction with efforts of WHOI/GOMTOX and CCS So what happened in 2009? – A moderate regional red tide, with toxicity in Mass Bay and Boston Harbor

  3. But first – the 2009 forecast

  4. Alexandrium Population Dynamics Model Cyst Dist. (# / cm^2) Endogenous Clock Germ. rate (% / day) Growth (per day) Growth = min ( f(PAR) , g(T,S) ) Upward swimming 10 m/day “Mortality” = 0.1 per day, with a temperature dependence

  5. 1997 2004 2005 2006 2007 2008

  6. Benthic Cyst 2009 Bloom ensemble seasonal forecast Hydrodynamics & meteorology Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5 2004 2005 2008 2006 2007 2008

  7. Impact of cyst abundance on the next year’s bloom (1997)

  8. 2005 2008 2006 2007 Shellfish harvesting closures

  9. 2009 Alexandrium chronology • March 24 – WHOI releases 2008 cyst data and predicts “moderately large” red tide for 2009 – comparable to 2006 • April 17 – Nauset system PSP toxicity closure • Late April - early May PSP toxicity observed in Maine and NH • May 7 – High PSP approaching closure levels at Star Island, NH • May 12th MWRA sampled for Alexandrium on regular nearfield survey (150 cells/L at N18) • MWRA conducted three ARRS surveys and a harbor survey • May 22 – North Shore and parts of Mass Bay closed • June 3 – Additional closure on South Shore • Abundances reached a maximum of 356 cells/L in late May – coincident with highest PSP toxicity • Bloom ended by June 8th survey

  10. May 20, 2009

  11. May 29, 2009

  12. June 8, 2009 – bloom over

  13. Boston Harbor Closed June 12th 2008 Boston Harbor counts. Boston Harbor sampled June 17th (cells gone a week later)

  14. Alexandrium abundance – MWRA nearfield area Contingency Plan Threshold Exceedance: >100 cells/L from May 12th to 29th (≤150 cells/L)

  15. Baywide Alexandrium Abundance2009 comparable to 2007

  16. Importance of winds for Mass Bay blooms

  17. 2009 2005 2006 2007 2008 5/4 5/14 5/24 6/3 6/13 6/23 GoMOOS Buoy A data supplied by Neal Pettigrew's group at the University of Maine

  18. 2005 2006 2007 Shellfish harvesting closures 2009 2008 2009

  19. Summary • Alexandrium population dynamics model & cyst abundance were good predictors of the magnitude of the 2009 bloom • Winds during the critical May – early June interval were light with only one small Northeasterly event. As a result, 2009 cell abundance in Mass Bay was relatively low, but still high enough to cause PSP closures (comparable in geographic extent to 2006, as predicted) • Early May winds transported cells into Massachusetts Bay, but unlike previous years, there were no subsequent storms and the bloom petered out. The 2009 bloom was offshore most of the season. • Shellfish toxicity within Massachusetts Bay seems to relate to transport of blooms from the north. There was no significant stimulation of Alexandrium cell abundance in the bay..

  20. Summary • Boston Harbor cell concentrations were low. This suggests that these populations are transported into the Harbor, and do not originate from in situ cyst germination and growth. • It will be interesting to see the results of the fall 2009 cyst survey. In past years, there has been an inverse relationship between the size of the bloom and the size of the resulting cyst population

  21. Impact of cyst abundance on the next year’s bloom (1997)

  22. Impact of bloom cell abundance on that year’s cyst abundance ??? (1997)

  23. Summary • We still believe we are in a “new era” of frequent and high levels of PSP toxicity in the western Gulf of Maine.

  24. Acknowledgements The data presented are the result of the efforts from a variety of intuitions and programs including: • MWRA/Battelle HOM6 team • WHOI scientists and GOMTOX Program (funded via NOAA/ Center for Sponsored Coastal Ocean Research/Coastal Ocean Program Grant #NA06NOS4780245) and the Woods Hole Center for Oceans and Human Health • MA DMF PSP data

  25. 1997 2004 2005 2006 2007 2008

  26. The 2009 Alexandrium fundyense bloom

  27. Summary • It will be interesting to see the results of the fall 2009 cyst survey. In past years, there has been an inverse relationship between the size of the bloom and the size of the resulting cyst population • We still believe we are in a “new era” of frequent and high levels of PSP toxicity in the western Gulf of Maine.

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